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Thirty Years of Breast Cancer Screening May Have Done More Harm Than Good

Posted Nov 25 2012 12:00am

A recent op-ed in the New York Times by H. Gilbert Welch, a co-author of Overdiagnosis, describes a tragedy of ignorance and overconfidence. The current emphasis on regular mammograms began thirty years ago. They will prevent breast cancer, doctors and health experts told hundreds of millions of women. They will allow early detection of cancers that, if not caught early, would become life-threatening. The campaign was very successful. According to the paper cited by Welch , about 70% of American women report getting such screening.

It is now abundantly clear this was a mistake. If screening worked perfectly if all of the cancers it detected were dangerous the rate of late-stage breast cancer should have gone down by the amount that the rate of early-stage breast cancer went up. Over the thirty years of screening, the rate of (detected) early-stage breast cancers among women over 40 doubled, no doubt because of screening. (Over the same period the rate of early-stage breast cancers among women under 40 barely changed.) In spite of all this early detection and treatment, the rate of late-stage breast cancer among women over 40 stayed essentially the same. All that screening (billions of mammograms), all that chemo and surgery and radiation, all that worry and time and misery and no clear benefit to the women screened and those who paid for the screening, treatment, and so on. Roughly all of the “cancers” detected by screening and then, at great cost, removed, aren’t dangerous, it turns out.

Quite apart from the staggering size of the mistake and the long time needed to notice it, screening has been promoted with specious logic.

Proponents have used the most misleading screening statistic there is: survival rates. A recent Komen Foundation campaign typifies the approach: “Early detection saves lives. The five-year survival rate for breast cancer when caught early is 98 percent. When it’s not? It decreases to 23 percent.” Survival rates always go up with early diagnosis: people who get a diagnosis earlier in life will live longer with their diagnosis, even if it doesn’t change their time of death by one iota.

Did those making the 98% vs. 23% argument not understand this?

I applaud Welch’s research, but his op-ed has gaps. A unbiased assessment of breast cancer screening would include not only the (lack of) benefits but also the (full) costs. Treatment for a harmless “cancer” may cause worse health than no treatment. Maybe chemotherapy and radiation and surgery increase other cancers, for example. What about the effect of all those mammograms on overall cancer rate? Welch fails to consider this.